Prime lens
Encyclopedia
In film and photography, a prime lens is either a photographic lens
whose focal length
is fixed, as opposed to a zoom lens
, or it is the primary lens in a combination lens system.
Confusion can sometimes result due to the two meanings of the term if the context does not make the interpretation clear. Alternative terms primary focal length, fixed focal length, and FFL are sometimes used to avoid ambiguity.
; that is, a prime lens is a fixed-focal-length, or unifocal lens, while a zoom lens has a variable focal length.
A prime lens of a given focal length is less versatile than a zoom whose range includes that focal length, but is often of superior optical quality, lighter weight, smaller bulk and lower cost. In comparison with a zoom lens, a prime lens has fewer moving parts which are optimized for one particular focal length. With a less complicated lens formula they suffer from fewer problems related to chromatic aberration
.
Because their optics are simpler, prime lenses usually have a larger maximum aperture
(smaller f-number
) than zoom lenses. This allows photography in lower light and a shallower depth of field
.
A normal lens
or "normal prime" is a lens with a focal length about equal to the diagonal size of the film or sensor format, or that reproduces perspective that generally looks "natural" to a human observer under normal viewing conditions.
, teleconverter
, or teleside converter
, the camera lens itself is properly called the prime lens. Prime is here used in the sense of primary, chief, original, first in order, etc.
Lens manufacturers such as ARRI Media, ISCO Precision Optics, Schneider
, Carl Zeiss AG, Canon and others still make variable focal length cine and video lenses regularly catalogued as variable prime lenses. A variable prime is sometimes distinguished from a "true zoom" in that the latter maintains focus as the focal length is varied.
This use of the term "prime lens" is an example of a retronym
. Early in photography only primary camera lenses were available, and were merely called "lenses" or "objectives". Later, "auxiliary" lenses were available, which usually fit in front of the front element of the primary, or "prime" lens.
.
, lenses with tilt and / or shift function, lenses with large apertures and macro
lenses.
Photographic lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...
whose focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
is fixed, as opposed to a zoom lens
Zoom lens
A zoom lens is a mechanical assembly of lens elements for which the focal length can be varied, as opposed to a fixed focal length lens...
, or it is the primary lens in a combination lens system.
Confusion can sometimes result due to the two meanings of the term if the context does not make the interpretation clear. Alternative terms primary focal length, fixed focal length, and FFL are sometimes used to avoid ambiguity.
As alternative to zoom lens
The term prime has come to be used as the opposite of zoomZoom lens
A zoom lens is a mechanical assembly of lens elements for which the focal length can be varied, as opposed to a fixed focal length lens...
; that is, a prime lens is a fixed-focal-length, or unifocal lens, while a zoom lens has a variable focal length.
A prime lens of a given focal length is less versatile than a zoom whose range includes that focal length, but is often of superior optical quality, lighter weight, smaller bulk and lower cost. In comparison with a zoom lens, a prime lens has fewer moving parts which are optimized for one particular focal length. With a less complicated lens formula they suffer from fewer problems related to chromatic aberration
Chromatic aberration
In optics, chromatic aberration is a type of distortion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have a different refractive index for different wavelengths of light...
.
Because their optics are simpler, prime lenses usually have a larger maximum aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
(smaller f-number
F-number
In optics, the f-number of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-number is the focal length divided by the "effective" aperture diameter...
) than zoom lenses. This allows photography in lower light and a shallower depth of field
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
.
A normal lens
Normal lens
In photography and cinematography a normal lens, also called a standard lens, is a lens that reproduces perspective that generally looks "natural" to a human observer under normal viewing conditions, as compared with lenses with longer or shorter focal lengths which produce an expanded or...
or "normal prime" is a lens with a focal length about equal to the diagonal size of the film or sensor format, or that reproduces perspective that generally looks "natural" to a human observer under normal viewing conditions.
Traditional meaning as primary lens
An alternate and apparently somewhat older meaning of the term prime lens is the main lens in a combination lens system. When the camera lens is used with some other optical device, such as a close-up lensClose-up lens
In photography, a close-up filter, close-up lens or macro filter is a simple secondary lens used to enable macro photography without requiring a specialised primary lens...
, teleconverter
Teleconverter
A teleconverter is a secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens...
, or teleside converter
Teleside converter
A teleside converter is a secondary lens which is mounted on the front of a photographic lens to increase the effective focal length of the lens they are attached to. They are used on cameras and video cameras with non–interchangeable lenses to increase the magnification of the image...
, the camera lens itself is properly called the prime lens. Prime is here used in the sense of primary, chief, original, first in order, etc.
Lens manufacturers such as ARRI Media, ISCO Precision Optics, Schneider
Schneider Kreuznach
Schneider Kreuznach is the abbreviated name of the company Jos. Schneider Optische Werke GmbH, which is sometimes also simply referred to as Schneider. They are a manufacturer of industrial and photographic optics....
, Carl Zeiss AG, Canon and others still make variable focal length cine and video lenses regularly catalogued as variable prime lenses. A variable prime is sometimes distinguished from a "true zoom" in that the latter maintains focus as the focal length is varied.
This use of the term "prime lens" is an example of a retronym
Retronym
A retronym is a type of neologism that provides a new name for an object or concept to differentiate the original form or version of it from a more recent form or version. The original name is most often augmented with an adjective to account for later developments of the object or concept itself...
. Early in photography only primary camera lenses were available, and were merely called "lenses" or "objectives". Later, "auxiliary" lenses were available, which usually fit in front of the front element of the primary, or "prime" lens.
Popular Focal Lengths
Many lens manufacturers produce or produced prime lenses at or near the following focal lengths: 20mm, 24mm, 28mm, 35mm, 50mm, 85mm, 105mm, 135mm, 200mm, 300mm, 400mm, 600mm. For prime lenses between 24mm and 200mm many manufacturers produce two or more lenses with the same focal length but with different maximum apertures to suit the different needs of photographers. Additional focal lengths can be created by using a teleconverterTeleconverter
A teleconverter is a secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens...
.
Specialist Lenses
Some specialist lenses are only available as prime lenses due to design or cost constraints. Examples of such specialist lenses are: extreme telephoto or wide angleWide Angle
Wide Angle is the debut studio album by British breakbeat trance producers Hybrid, and was re-released in 2000 as a double-CD edition entitled Wider Angle...
, lenses with tilt and / or shift function, lenses with large apertures and macro
Macro photography
Macrophotography is close-up photography, usually of very small subjects. Classically a macrophotograph is one in which the size of the subject on the negative is greater than life size. However in modern use it refers to a finished photograph of a subject at greater than life size...
lenses.
External links
- Photo Dictionary definition
- Zoom vs. Prime Lenses
- Prime lenses and zooms compared with photographs to illustrate